Field of the Invention
The present invention relates to a wafer processing apparatus to divide a wafer.
Description of the Related Art
As a method for dividing a wafer, the following method has been proposed. Specifically, a modified layer is formed inside a workpiece by irradiating a wafer with a pulsed laser beam having capability of transmission through the wafer, with the light focus point set inside the area along which dividing should be performed. Thereafter, the wafer is divided by applying an external force to the wafer along planned dividing lines, along which the strength is lowered due to the forming of the modified layer (refer to e.g. Japanese Patent Laid-Open No. 2002-192367). As a method for applying the external force to the wafer in which the modified layer has been formed, there has been proposed a method in which the wafer is disposed in a liquid tank and ultrasonic waves generated by an ultrasonic oscillator are made to act on the wafer (refer to e.g. Japanese Patent Laid-Open No. 2005-135964).